This SP barrel is one of the best barrels out there, i have tested lots of barrels including
Stiffi, CP 1 and 2 piece, assassin barrel, J&J, DYE, PROTO, and lots more. Its deadly accurate, quiet (on my rail), cleans breaks nicely, what else can you expect from a barrel. I think the whole insert/barrel backs matching your paintballs is just so the company can make money. just make sure the your paintballs are to big for your barrel. i would suggest getting a .689 insert for your smaller paintballs and a .691 for the bigger paintballs. Its a great barrel, you can go wrong with it.